PIG DECOMP: Baseline data for northeastern Ohio

25 June 2007: While we are doing the bear decomposition study, we decided to put a domestic pig out in an area nearby. Laura Bock above has just placed the carcass out on the afternoon of 25 June. Pigs are often used during studies of forensic entomology because the body size, body cavity size, percent hair coverage, and other characters make pigs very similar to humans in terms of decompositional patterns. We will be gathering insect succession data, and keeping track of fly development to better hone our information on local insect forensic indicators.

25 June 2007: Like the bear, we placed caging around the pig to keep out large scavengers. We want to keep the bones to add to the Museum's osteology collection. Note that the frame of the cage has short legs, creating a space for wandering maggots to egress at a later date.

25 June 2007: Things happen fast at summer temps. Two hours after placement, we already have hundreds of female flies laying eggs (ovipositing) on the pig around the orifices of the head and anus.

26 June 2007: Less than 24 hours after placement, eggs have hatched and maggots are making fast work of the snout. Note the light area under the chin is actually an egg mass. The eyes, mouth, and nostrils are choked with 10's of thousands of maggots. The blow flies Lucilia illustris (a green bottle fly) and Phormia regina (the black blow fly) constitute the majority of these maggots.

27 June 2007: Two days into decomp the head is being rapidly consumed. The body is showing considerable swelling from bacterial gasses in the abdomen. Carrion and rove beetles are present hunting maggots.

28 June 2007: By day three the maggots are getting large and breaking the body down at a horrendously fast pace. The smell is awful, and the liquids of putrefication are staining the ground black. The maggot mass temperature, like with the bear, is 18 degrees C above ambient.

29 June 2007: By the fourth day, many maggots have matured and are leaving the carcass. The masses of maggots at the head and anus have appeared to meet in the middle, as the main body cavity is greatly decomposed. We have collected many maggots in ethanol, kept many alive in breeding containers (we're still using our nearby insectary), and have swept scores of adult flies to facilitate identification. We have been taking beetle adults and larvae using forceps.

The dry phase of decomposition

29 June 2007: During this period of very slow decomposition, we do have occasional colorful visitors as shown in the photo above. This is a question mark, a type of brush-footed butterfly (family Nymphalidae). Butterflies and moths visit every so often to sip on the moisture present on or in some parts of the carcass. These liquids are going to be rich in nutrients, and help insects we normally associate with plant pollination develop energy and nutrient reserves to aid with movement and egg production.

We have witnessed and recorded a shift in the fly fauna. The dominant taxon present is the sepsid fly Nemopoda nitidula. Not much is known about this fly, although it has been associated with carrion in the past. I have taken it in carrion-baited traps, and reared it from maggots on a dead bat in a cave. Their value as a forensic indicator is presently unknown.

A month into decomposition...

23 June 2007: As you can see from the image above, not much has changed over the past week. We collected intensively yesterday, and here is the fauna:

FLIES: 3 blow fly puparia, a few adults of Phormia regina, piophilid flies (Prochyliza sp. and Stearibia nigriceps), some undetermined muscoid adults, and some maggots that are presumably the black dump fly.

BEETLES: first adult of the carrion beetle Nicrophorus tomentosus, the sap beetles Omosita colon and Necrobia rufipes, larvae of the silphid genus Necrodes, and miscellaneous rove beetles.

We are confident so far that we can apply the same data on insect development that we use on human victims to cases of black bear poaching. We still need to be careful about interpreting the faunal succession (change over time). To help with this, we are placing a pig out in the vicinity of this black bear to document the faunal succession there. That begins tomorrow afternoon (Monday, 24 June), and should last about a month. Again, the bones from the pig will be accessioned into the Museum's osteology collection.

Data from rearings

17 June 2007: Not much new happening on the bear itself. Still some small flies and carrion beetles, but with some rain this morning we observed a few black blow flies (Phormia regina) exploring the surface of the carcass.

17 June 2007: On the other hand, our rearings of insects taken from the carcass or wandering from the carcass are yielding good data! The idea is simple. Maggots are relatively challenging to identify to species. We collect maggots, but simultaneously place living ones on raw beef in containers to raise the maggots to the puparial and then the adult stage. This helps narrow the possible range of taxa represented by the maggot collections.

Our techniques are nothing special. We take some damp paper towel and in it place a cube of beef approximately 1"x1"x1". This is wrapped loosely in some aluminum foil, and this packet is then placed on top of some vermiculite or saw dust. When the maggots mature, they will wander off the meat (just like they do on the carcass) and move the saw dust to form the puparium. We have to continually check the packet, as some maggots don't go far and form a puparium in the foil. These are just removed and placed in the saw dust.

If we have maggots moving off the carcass, we collect these too, and place them in separate containers with the date and time of collection. The maggots are put into a pile of saw dust and allowed to pupate. The photo above represents the results of collecting 75 wandering maggots collected about a week ago. All appear to be Phormia regina. I placed this container in the freezer today, and will leave overnight. They will then be taken to the lab for identification and recording of data. Some representative specimens will be mounted on pins, labelled, and placed in the forensic entomology collection of the Cleveland Museum of Natural History.

Approaching the first month of decomp

15 June 2007: The majority of active insects consist of silphid (carrion) beetles hunting soft-bodied invertebrates, black dump fly maggots (predators of other maggots), various beetles interested in dry tissues, miscellaneous yet-to-be-determined minute dung flies of the family Sphaeroceridae, 3 species of Sepsid flies (Enicomira, Sepsis, and Nemopoda), and 3 species of Piophilid flies (Piophila, Prochyliza, and 1 undet. genus). Sweeping over the bear yields mostly the small flies (Sphaeroceridae, Piophilidae, and Sepsidae).

The underside of the bear is still moist. This is where the black dump fly maggots and most of the carrion beetle larvae are. We are supposed to get rain this weekend, and that could change some of the activity dynamics. For instance, maggots and beetle larvae may move to the surface, or we may get a new generation of flies hitting the carcass.

13 June 2007: At this point, insect activity is greatly slowed and our efforts include mostly sweeping small flies from the carcass with an insect net, or as Laura is demonstrating we use forceps to nab beetles and beetle larvae from the surface of the carcass. We carefully lift the legs and head to expose the moist areas under the carcass where there is still some maggot activity, and invertebrate predators are still common.

Dry Times: 5-10 June 2007

10 June 2007: Decomposition is greatly slowed... Here is what we have learned so far:

1. We had 3 major mass movements of maggots off the carcass. The middle wave had by far the most maggots (4 June). The last wave was the least dense.
2. The same insects we expect on human corposes are also found on the bear.
3. Seemingly because of the dense fur and mass of the body, decomposition progressed somewhat differently with all of the maggot movement off the carcass originating around the abdomen.



9 June 2007: Very little blow fly activity is present (maggots and adults).

7 June 2007: Today, we saw the last (third) wave of wandering maggots leave the body. Dr. Dan Palmer of John Carroll University is a computer scientist specializing in swarm behavior, a means of analyzing group dynamics and their subsequent emergent properties.

7 June 2007: Here is the last wave... The first wave was more dense than this, and the second wave from 4 June 2007 (see below) was the most dense. This last wave composed the least number of maggots moving off synchronously.

7 June 2007: Dr. Palmer noticed that those individuals that were separate from a group simply oriented themselves away from the exclosure. Those within groups were positioned haphazardly, but the mass itself made consistent progress away from the carcass. This opens up new possible questions in using swarm theory to describe wandering maggot behavior!

5-6 June 2007: Very little bug activity (relatively speaking) is present. Sepsid and piophilid flies are still active, as are some muscids. Silphid larvae are common, and nitidulid adults are abundant at this time.

14 Days into Decomp...

4 June 2007: The maggot masses are moving off of the bear. the abodomen and mouth/nose remain highly active. Nearby 'waves' of maggots are not nearly as huge as earlier observations.

4 June 2007: Our insectary. About 100 feet from the carcass, we rear immatures collected from the bear to help facilitate identification of material collected from the bear. The location of the maggots on the bear is recorded (e.g., collected from mouth, collected wandering from carcass, etc.). Live maggots are given raw beef.

Week 2: 2-3 June 2007: Huge Maggot Exodus

An incredible sequence of maggot migration...

3 June 2007: Rain has created a situation where maggots are creating large amounts of 'froth' around the edge of the bear.

3 June 2007: Maggots are moving in an enormous exodus from the bear. We began to see this to a smaller degree several days ago, but now they are grouping together in a virtual maggot swarm.

3 June 2007: A close-up of maggots on the trail...

3 June 2007: A maggot's-eye view of the exodus of the carcass. The maggots remaining on the bear are probably somewhat younger. Many early instars of blow flies are still present on the carcass. There will probably be another substantial mass movement of maggots of the carcass in upcoming days.

3 June 2007: During the study, we have been keeping track of maggot development. At the bottom is a mature maggot. Above that is a newly formed pupa (hours old), followed by a darker puparium a day or so old, followed by progressively darker (and older) puparia.

2 June 2007: In the morning, many maggots are mature and actively moving. This appears to be in preparation for a mass migration off the carcass. The stench is still horrendous, and the vegetation is dying around the bear.

2 June 2007: The first real "wave" of maggots leaving the carcass. Many maggots continue to grow an develop on the carcass. Adult flies (Calliphoridae, Muscidae, Sepsidae, Piophilidae) are still active on and around the bear.

2 June 2007: A maggot's- eye view of the trail...

31 May - 1 June: Maggot activity increasing

1 June 2007: Here is the bear, with expansive coverage by feeding maggots, 11 days into the decompositional process. What have we learned so far?

1 - There are many similar patterns seen on the bear that we see in pig or human decomposition, such as flies laying eggs on or within orifices (mouth, nose, anus, etc.), early activity by green bottle flies of the tribe Luciliini (e.g., Phaenicia) followed by the black blow fly (Phormia regina), beetle activity occurring slightly after flies arrive, and the subsequent arrival of small flies after blow flies have 'conditioned' the carcass (e.g., Piophilidae, Sepsidae).

2 - There is a slight delay in maggot activity compared to humans or pigs. This may be for two reasons: a) the expansive coverage of fur, and/or b) the freezing of the carcass prior to the study may have altered the tissues enough to make them less-than-ideal for attracting egg-laying flies.

3- At about day 10, herbaceous plants (e.g., Virginia creeper) near the bear begin to turn brown when decompositional fluids saturate the soil.

1 June 2007: Maggot activity on the head has literally exploded.

1 June 2007: A close-up of the maggot mass centered in the mouth and nose. When we took outside temperature readings it was 27.5 degrees C. Placing the bulb of the thermometer into any of the maggot masses gave a reading of 46.0 degrees C - nearly 20 degrees warmer!

Maggot mass temperatures are important. They occur from the normal metabolism of feeding maggots (movement, feeding, digestion, etc.) and warm the carcass. This increased temperature probably helps to accellerate maggot development.

31 May 2007: The maggot mass covers most of the body. Fur is being deposited by maggot action in a circle around the bear.

31 May 2007: The head orifices are still a key point of maggot activity.

31 May 2007: Our observations show that the migration of maggots from the body (to find a safe place in the soil to form the pupa, or in flies pupariate) occurs most heavily early in the morning. By mid day, when temperatures are high, dessication is possible, and visual predators are abundant, the migrational activity is at its minimum. This photo was taken about 8:00AM.